1. Field of the Invention
The present invention relates to a substrate heating apparatus heating a substrate.
2. Description of the Related Art
In semiconductor manufacturing processes and the like, a ceramic heater including a disk-shaped ceramic base, in which a linear resistance heating element is buried, is widely used as a substrate heating apparatus.
As the method of heating a substrate, recent semiconductor manufacturing processes actively use non-contact type lamp heating using a halogen lamp or the like as well as the contact type heating using the ceramic heater. In the cases of using the lamp heater, the ceramic heater is often used together for supplementarily heating the substrate.
In the semiconductor manufacturing processes, to increase a production yield, it is required to equalize substrate surface temperature with high accuracy. The ceramic heater is therefore required to perform fine temperature adjustment according to an environment around the substrate. For example, a multi-zone heater, in which the inside of the ceramic base is divided into a plurality of zones and a suitable heating value is set for each zone has been examined (Japanese Patent Laid-Open publication No. 2001-52843). With the multi-zone heaters, a heating value is optimally adjusted according to locations in a substrate mounting surface. The Japanese Patent Laid-Open publication No. 2001-52843 has proposed a multi-zone heater in which the ceramic base is divided into nine zones each including a resistance heating element buried therein. In any one of the conventional multi-zone heaters, the plurality of resistance heating elements are buried in the single-piece base.
However, in the multi-zone heaters in which the heating value varies by location, hot and cold sections are locally formed in the conventional single-piece base. Accordingly, local stress is more likely to generate in the base with the resistance heating elements buried therein. The ceramic base, in particular, has a tendency to be more sensitive to tensile stress than to compressive stress. The peripheral parts of the hot and cold sections in which tensile stress generates are more likely to damage.
Not only the ceramic heater but also a substrate heating apparatus using metal or resin for the base on which a substrate is placed involves the problem of stress generation due to the difference in temperature settings by location.